US9026383B2ActiveUtilityA1
Flow rate sensor
Est. expirySep 30, 2029(~3.2 yrs left)· nominal 20-yr term from priority
G01F 1/6847G01F 1/698G01F 1/69G01F 1/36G01F 1/6842G01F 1/88
24
PatentIndex Score
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Cited by
25
References
5
Claims
Abstract
A flow rate sensor is disclosed, comprising a flow rate calculation part that calculates a flow rate of a fluid based on an expression using X d /X u that satisfies an expression at least in a certain range of the flow rate when an output of a constant temperature control circuit corresponding to an upstream resistor is defined as V u , an output of a constant temperature control circuit corresponding to a downstream resistor is defined as V d , and the flow rate is defined as and the flow rate calculation part corrects the zero point output as being an output when the flow rate is zero by using a zero offset function (OFS) defined as a function of V u +V d X d /X u .
Claims
exact text as granted — not AI-modifiedThe invention claimed is:
1. A flow rate sensor wherein two resistive elements whose resistance values change in accordance with a temperature of a fluid are arranged in an upstream side and a downstream side in a channel where the fluid flows, and two constant temperature control circuits each of which contains these resistive elements respectively are arranged so that a temperature of the resistive elements is controlled at a constant by the constant temperature control circuits, the flow rate sensor comprising:
a flow rate calculation part that calculates a flow rate (Q) of the fluid based on an expression (Expression 2) using X d /X u that satisfies an expression (Expression 1) at least within a range of the flow rate (Q) when an output of the constant temperature control circuit corresponding to the upstream resistive element is defined as V u , an output of the constant temperature control circuit corresponding to the downstream resistive element is defined as V d , and the flow rate of the fluid is defined as (Q), wherein
the flow rate calculation part corrects a zero point output as being an output when the flow rate (Q) is zero by using a zero offset function (OFS) defined as a function of V u +V d X d /X u
ⅆ
V
u
ⅆ
Q
≅
ⅆ
(
V
d
X
d
/
X
u
)
ⅆ
Q
[
Expression
1
]
Q
=
(
V
u
-
V
d
V
u
+
V
d
X
d
/
X
u
+
OFS
)
SENSx
[
Expression
2
]
where (OFS) is the zero offset function, and (SENSx) is a conversion function that converts a calculation value of an output from each constant temperature control circuit into a flow rate.
2. The flow rate sensor described in claim 1 , wherein
the flow rate calculation part calculates the flow rate (Q) by the use of the conversion function (SENSx) defined as a function of V u +V d X d /X u .
3. The flow rate sensor described in claim 1 , wherein
the flow rate calculation part calculates the flow rate (Q) based on an expression [Expression 4] wherein a temperature correction term is further added to the expression
Q
=
{
V
u
-
V
d
V
u
+
V
d
X
d
/
X
u
[
1
+
a
(
V
u
+
V
d
X
d
/
X
u
V
ut
+
V
dt
X
dt
/
X
ut
)
]
+
OFS
}
SENSx
[
Expression
4
]
where V ut is an output at a previously measured predetermined temperature of the constant temperature control circuit corresponding to the upstream resistive element, V dt is an output at a previously measured predetermined temperature of the constant temperature control circuit corresponding to the downstream resistive element, and X dt /X ut satisfies the expression [Expression 1] regarding V ut and V dt .
4. The flow rate sensor described in claim 1 , wherein
the conversion function (SENSx) is a calibration curve.
5. The flow rate sensor described in claim 1 ,
further comprising a temperature calculation part that calculates an ambient temperature based on V u +V d X d /X u .Cited by (0)
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